PHILADELPHIA—Grossly underestimating the patience of their audience, rock-and-blues band Flashback Depot was going to pay dearly Thursday for attempting to perform an original song during their hour-long set. “Some people say we sound a little like the E Street Band, but we’ll let you be the judge of that,” said frontman Eric Saunders, who would forever rue the moment he decided to add a new self-penned single to the band’s lineup of rock standards, prompting dozens of patrons to step outside for a smoke break and several more to close their bar tabs as the group squandered the goodwill it had built during the past half hour by playing adequate covers of “All Small Things” and “Personal Jesus.” “We’ve actually never played this one live, so it might be a little shaky.” The band was eventually escorted out of the bar after debuting a six-minute power ballad written by their drummer.